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While squirrels’ daring dash across roadways may seem like a quirk, it is actually a defensive tactic designed to evade predators. Yet another fascinating behavior is their selective approach to nuts—some are gobbled up on the spot, while others are hidden away for later. Researchers are still untangling the logic behind these decisions, and several theories point to consumption time, perishability, and tannin content as key factors.
In a 1992 study published in Animal Behaviour, Dr. Lucia F. Jacobs observed five hand‑raised grey squirrels presented with shelled hazelnuts and laboratory rodent chow. The squirrels appeared to gauge the time required to eat each food item and opted for the less time‑intensive choice. They consumed the hazelnuts immediately, but cached the chow—despite the fact that the chow would spoil faster than the nuts. This suggests that squirrels balance immediate gratification against the effort needed to eat.
Contrary to Jacobs’ findings, a 1996 study in Animal Behaviour found that decay rate does influence caching decisions. Nuts have a limited shelf life: red oak acorns germinate in spring after winter dormancy, making them more resilient, whereas white oak acorns sprout in fall and spoil more quickly. When free‑range grey squirrels were offered both types, they ate white acorns promptly and buried red acorns, even removing the embryo to prevent germination and extend storage life. This indicates that squirrels use perishability as a primary cue when deciding whether to cache.
Nuts contain tannins—natural polyphenols that can inhibit digestive enzymes and impair nutrient absorption. High tannin levels can lead to malnutrition, dehydration, ulcers, and kidney issues. Studies show that burying high‑tannin foods allows tannins to leach out over time, reducing toxicity. In 1986, researchers added tannins to white oak acorn‑based food and found that grey squirrels preferred the lower‑tannin mixture. Although the high‑tannin food did not visibly harm protein digestion, the researchers speculate that squirrels use tannin levels as a proxy for decay rate.
In sum, squirrels likely weigh multiple factors—how long it takes to eat, how quickly the food will spoil, and its tannin content—when deciding whether to bury a nut or consume it immediately.
